Various forms of commercial equipment include rotating components. For example, a typical gas turbine includes an axial compressor at the front, one or more combustors around the middle, and a turbine at the rear. The compressor generally includes a casing that surrounds and encloses alternating stages of circumferentially mounted stator vanes and rotating blades. The stator vanes typically attach to the casing, and the rotating blades typically attach to a rotor inside the compressor. Ambient air enters the compressor, and each stage of stator vanes directs the airflow onto the following stage of rotating blades to progressively impart kinetic energy to the working fluid (air) to bring it to a highly energized state. The working fluid exits the compressor and flows to the combustors where it mixes with fuel and ignites to generate combustion gases having a high temperature and pressure. The combustion gases exit the combustors and flow to the turbine where they expand to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
The rotating blades in the compressor typically connect to the rotor in a manner that allows the rotating blades to be periodically removed for maintenance, inspections, and/or replacement. For example, the rotating blades may include a root or base that slides into a complementary dovetail slot in the rotor. The complementary surfaces between the root and the dovetail slot prevent each blade from moving radially, and the area on the rotor surrounding the slot may be “staked” or plastically deformed to prevent the root from moving axially in the slot. In this manner, each rotating blade may be removed from the rotor, and the same or a replacement blade may be re-inserted into the dovetail slot before the rotor is re-staked to hold the blade in place.
The area on the surface of the rotor suitable for staking the blade is finite and will therefore permit removal and re-staking of the blade a limited number of times. As a result, various systems and methods have been developed to modify the rotor to permit the blades to be removed and re-staked multiple times. For example, U.S. Patent Publication 2009/0077795, assigned to the same assignee as the present application, describes a system and method in which a drill is used to create a recess in the bottom of the slot. An insert may then be placed in the recess and staked to hold the blade axially in place. In the event that the blade must be removed from the rotor again, a new insert may be used to again stake the blade axially in place.
The modification to the slot in the rotor typically requires substantial disassembly of the compressor and associated equipment to provide suitable access to the rotor. For example, the casing surrounding the rotating blades is often completely removed, and scaffolding is erected around the rotor to support the equipment and personnel performing the modification. In addition, the gas turbine itself may be situated in a building having walls and/or a roof that must be removed or otherwise opened to provide sufficient access to the rotor. This disassembly and staging is expensive to perform, extends the time needed for the rotor modification, and increases the outage associated with the modification. Therefore, an improved system and method for modifying the slot in the rotor that reduces the amount of disassembly of the compressor and staging would be useful.